Not really odd. We seem to have similar 1e (AD&D) timelines, but different experiences.
First, multiclassing. Multiclassing did exist- for demihumans. And without going into EGG's preferences, the rules for multiclassing were terrible with the level limits for those demihumans (that's before you get into the whole elves can't be resurrected, etc.). Since there is nothing comparable in 5e, that's a bad example.
Dual classing didn't exist in any campaigns I knew of. Not a single one, due to the implementation (you "forgot" your class until you equaled the level). Now, I have since heard that there were a few groups that, pace a video game, had players choose one level in a class, then dual class in another, but that was foreign to the campaigns I knew of and (to the extent someone did it) that would have been disallowed- and there were no examples I saw in tournament play- and I never saw a "real" bard. YMMV.